Display device

ABSTRACT

A display device is provided and includes substrate; first and second common electrodes arranged on the substrate; pixel electrodes arranged over first and second common electrodes; insulating layer arranged between pixel, first common, and second common electrodes; first line having first and second terminals, first terminal connected to first common electrode; second line having first and second terminals, first terminal connected to second common electrode; first transistor connected to second terminal of first line; and second transistor connected to second terminal of the second line, wherein first and second common and pixel electrodes are arranged in display area, first and second transistor are arranged outside display area, second line is longer than first line, and channel width of first transistor is smaller than channel width of second transistor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/956,329 filed on Apr. 18, 2018, which is basedupon and claims the benefit of priority from Japanese Patent ApplicationNo. 2017-083862, filed Apr. 20, 2017, the entire contents of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to a display device withan inputting function.

BACKGROUND

Mobile terminals such as smart phones, tablet PCs and notebook computershave been prevalent. A mobile terminal includes a flat display deviceusing liquid crystal or organic EL elements. The display device isconnected to a host device which outputs image data, commands, and thelike. The display device includes a display panel and a driverprocessing commands and driving the display panel.

In the display device, pixels two-dimensionally arrayed on the displaypanel include a common electrode and a pixel electrode, and the liquidcrystal or organic EL elements are arranged between the common electrodeand the pixel electrode. When the driver writes a pixel signal to thepixels on the display panel, the liquid crystal or organic EL elementsarranged between the common electrode and the pixel electrode arecontrolled and an image is thereby displayed.

Display devices capable of detecting an inputting object such as afinger and a touch pen (also called a stylus) approaching or contactingthe screen have been widely employed. The operation of allowing theinputting object to approach or contact the screen is called a touchoperation or a touch, and the detection of a position of the inputtingobject is called touch detection. Examples of the touch detectioninclude various types such as an optical type, a resistive type, acapacitive type, and an electromagnetic induction type. The capacitivetype utilizes a feature that the electrostatic capacitance between apair of electrodes (called a drive electrode and a detection electrode)is varied by approach or contact of the inputting object, and hasbenefits that the structure is comparatively simple and that the powerconsumption is small.

If the number of drive electrodes and the detection electrodes isincreased to improve the performance of the image display operation andthe touch detection operation, in the display device with the touchdetection function, a layout of lines connected to the electrodes or aterminal layout of a semiconductor chip controlling the image displayoperation and the touch detection operation becomes complicated. Inaccordance with this, the number of terminals of the semiconductor chipis increased, the size of the semiconductor chip becomes larger, and thestructure becomes complicated.

SUMMARY

The present application generally relates to a display device.

According to one embodiment, a display device includes a display unitincluding electrodes, a touch sensor configured to supply drive signalsto the electrodes and receive signals from the electrodes, and a switchcircuit group including transistors connected between the touch sensorand the electrodes. The transistors include a first transistor connectedto a first electrode via a line of a first length and a secondtransistor connected to a second electrode via a line of a second lengthlonger than the first length. The channel width of the first transistoris smaller than a channel width of the second transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a schematic configuration of anexample of a display device according to an embodiment.

FIG. 2 is a plan view showing an example of the display device.

FIG. 3 is a cross-sectional view showing an example of a first substrateSUB1 of the display device.

FIG. 4 is a plan view showing an example of arrangement of commonelectrodes CE of the display device.

FIG. 5 is a circuit diagram showing an example of a pixel PX of thedisplay device.

FIG. 6 is a circuit diagram showing an example of self-capacitive touchdetection.

FIG. 7 is a circuit diagram showing an example of the self-capacitivetouch detection.

FIG. 8 is a circuit diagram showing an example of the self-capacitivetouch detection.

FIG. 9 is a circuit diagram showing an example of the self-capacitivetouch detection.

FIG. 10 is a circuit diagram showing an example of the self-capacitivetouch detection.

FIG. 11 is a signal waveform chart showing an example of theself-capacitive touch detection.

FIG. 12 is a circuit diagram showing an example of an operation of aswitch circuit group SWG for CDM drive.

FIG. 13 is a circuit diagram showing details of an example of the switchcircuit group SWG.

FIG. 14 is a circuit diagram showing a principle of an example of theCDM drive.

FIG. 15 is a signal waveform chart showing an example of the CDM drive.

FIG. 16 is a circuit diagram showing an example of TFT of the switchcircuit group SWG.

FIG. 17A is a circuit diagram showing a channel width of TFT of theswitch circuit group SWG.

FIG. 17B is a circuit diagram showing a channel width of TFT of theswitch circuit group SWG.

FIG. 18 is a circuit diagram showing an example of a layout of thecommon electrodes and the switch circuit group SWG.

FIG. 19 is a circuit diagram showing another example of a layout of thecommon electrodes and the switch circuit group SWG.

FIG. 20 is a circuit diagram showing yet another example of a layout ofthe common electrodes and the switch circuit group SWG.

FIG. 21A is a diagram showing an example of a layout of drive signallines on first substrate SUB1.

FIG. 21B is a diagram showing another example of a layout of drivesignal lines on first substrate SUB1.

FIG. 22A is a diagram showing still another example of a layout of thedrive signal lines on the first substrate SUB1.

FIG. 22B is a diagram showing still another example of a layout of thedrive signal lines on the first substrate SUB1.

FIG. 22C is a diagram showing still another example of a layout of thedrive signal lines on the first substrate SUB1.

FIG. 23A is a diagram showing yet another example of a layout of thedrive signal lines on the first substrate SUB1.

FIG. 23B is a diagram showing yet another example of a layout of thedrive signal lines on the first substrate SUB1.

FIG. 23C is a diagram showing yet another example of a layout of thedrive signal lines on the first substrate SUB1.

DETAILED DESCRIPTION

Embodiments will be described hereinafter with reference to theaccompanying drawings. The disclosure is merely an example and is notlimited by contents described in the embodiments described below.Modification which is easily conceivable by a person of ordinary skillin the art comes within the scope of the disclosure as a matter ofcourse. In order to make the description clearer, the sizes, shapes andthe like of the respective parts may not be illustrated as they are, butmay be changed and illustrated schematically in the drawings, andhatching attached to distinguish structures may be omitted. Constituentelements corresponding to each other in a plurality of drawings may bedenoted by similar reference numerals and their detailed descriptionsmay be omitted unless necessary.

In general, according to one embodiment, a display device includes adisplay unit including electrodes two-dimensionally arrayed on asubstrate, a touch sensor configured to supply drive signals for touchdetection to the electrodes and receiving the signals from theelectrodes, and a switch circuit including transistors connected betweenthe touch sensor and the electrodes to select at least one of theelectrodes. The transistors include a first transistor connected to afirst electrode of the electrodes via a line of a first length and asecond transistor connected to a second electrode of the electrodes viaa line of a second length longer than the first length. A channel widthof the first transistor is smaller than a channel width of the secondtransistor.

The display device equipped with the touch detection function includesan on-cell type (also called an external type) in which the displaydevice and the touch panel implementing the touch function are producedseparately and the touch panel is bonded to the screen of the displaydevice, and an in-cell type (also called a built-in type) in which thedisplay device and the touch panel are integrated. The in-cell typedisplay device includes a device in which several or all parts havingthe touch detection function also serve as several or all parts havingthe display function or a device in which a component having the touchdetection function and a component having the display function do notserve each other. In the in-cell type display device, for example, thedetection electrode is formed between a color filter and a polarizer,and a common electrode formed on a TFT substrate is also served as adrive electrode. Since the in-cell type display device includes noexternal touch panel, the display device is entirely slim andlightweight, and visibility of the display is also improved. Embodimentsof the in-cell type display device will be explained. However, theembodiments can also be applied to an on-cell type display device.

Examples of the touch detection include various types such as an opticaltype, a resistive type, a capacitive type, and an electromagneticinduction type. The capacitive type utilizes a feature that theelectrostatic capacitance between a pair of electrodes (called a driveelectrode and a detection electrode) is varied by approach or contact ofthe inputting object, and has benefits that the structure iscomparatively simple and that the power consumption is small. A displaydevice equipped with a capacitive touch detection function will beexplained as the embodiments. However, the embodiments can be applied tonot only the capacitive type touch detection, but also the touchdetection of the other types such as an electromagnetic induction type.

The capacitive type includes a mutual-capacitive type (mutual capacitivesensing) for detecting an electrostatic capacitance between twodetection electrodes opposed to be spaced apart from each other and aself-capacitive type (self-capacitive sensing) for detecting anelectrostatic capacitance between one detection electrode and, forexample, a reference electrode having a reference potential such as aground potential. The self-capacitive sensing will be explained as anexample, but the embodiments can also be applied to a display devicewhich executes mutual-capacitive touch detection. In the self-capacitivesensing, the reference electrode may be a conductive pattern of beingdisposed around the detection electrode in a remote distance to form anelectrostatic capacitance which can be detected between the referenceelectrode and the detection electrode. A path for supplying a fixedpotential may be connected to the reference electrode. The shape and thelike of the reference electrode are not particularly limited. Thedisplay device with the touch detection function is an aspect of theinput device, and detects an input signal and calculates a touchposition when a finger or an input instrument such as a stylus touchesor approaches the touch surface. The touch position is coordinates of apoint at which the input signal is detected, on the touch surface.

A liquid crystal display device, an organic EL display device, a plasmadisplay device, and the like can be used as the display device and, theembodiments using the liquid crystal display device will be explainedhereinafter as an example, but the embodiments can also be applied tothe organic EL display device, the plasma display device, and the like.The display mode of the liquid crystal display device is largelyclassified into two modes in accordance with the direction ofapplication of the electric field to vary the alignment of liquidcrystal molecules of a liquid crystal layer which is a display functionlayer. The first mode is what is called a longitudinal electric fieldmode in which the electric field is applied in a thickness direction (oran out-of-plane direction). The longitudinal electric field modeincludes, for example, twisted nematic (TN) mode, vertical alignment(VA) mode, and the like. The second mode is what is called a lateralelectric field mode in which the electric field is applied in a planedirection (or an in-plane direction). The lateral electric field modeincludes, for example, in-plane switching (IPS) mode, fringe fieldswitching (FFS) mode which is a type of the IPS mode, and the like. Theembodiments explained below can be applied to any one of thelongitudinal electric field mode and the lateral electric field. Thedisplay device of the lateral electric field will be explained as theembodiments, but the embodiments can also be applied to the displaydevice of the longitudinal electric field.

First Embodiment

-   -   [Schematic Configuration]

FIG. 1 is a perspective view showing an overall schematic configurationof an example of a display device equipped with a touch detectionfunction according to the embodiment. The display device includes adisplay panel PNL including a touch detection mechanism, a touch sensingchip TSC, and a driver chip DRC. The display panel PNL includes atransparent first substrate SUB1 formed of glass, resin, and the like, atransparent second substrate SUB2 formed of glass, resin, and the likeand disposed to be opposed to the first substrate SUB1, and a liquidcrystal layer (not shown) disposed between the first substrate SUB1 andthe second substrate SUB2. Since pixels (shown in FIG. 5) are disposedin two-dimensional array (also called a matrix) in the X direction andthe Y direction on the first substrate SUB1, the first substrate SUB1 isalso called a pixel substrate or an array substrate. The secondsubstrate SUB2 is also called a counter-substrate. The display panel PNLis observed from the second substrate SUB2 side. For this reason, thesecond substrate SUB2 may be called an upper substrate while the firstsubstrate SUB1 may be called a lower substrate.

The display panel PNL is shaped in a rectangular flat plate, and itsshorter side is along an X direction and its longer side is along a Ydirection. The first substrate SUB1 and the second substrate SUB2 aresubstantially the same in size of the shorter side but different in sizeof the lower side. The longer side of the first substrate SUB1 is largerthan the longer side of the second substrate SUB2. Since a first shorterside of the first substrate SUB1 and a first shorter side of the secondsubstrate SUB2 are aligned, a second shorter side of the first substrateSUB1 protrudes further than a second shorter side of the secondsubstrate SUB2 in the Y direction. The driver chip DRC which drives thedisplay panel PNL for image display is mounted on a portion of the firstsubstrate SUB1 protruding further than the second substrate SUB2 in theY direction. The driver chip DRC is also called a driver IC or a displaycontroller IC. An area where the pixels are disposed in two-dimensionalarray is called a display area DA (or an active area), and a non-displayarea NDA other than the display area DA is also called a frame area.

The display device can be connected to a host device HOST. The displaypanel PNL and the host device HOST are connected to each other via twoflexible printed circuits FPC1 and FPC2. The host device HOST isconnected to the first substrate SUB1 via the flexible printed circuitFPC1. The touch sensing chip TSC which controls the touch detection is aChip on Film (COF) chip disposed on the flexible printed circuit FPC1.The touch sensing chip TSC is also called a touch detector IC or touchcontroller IC. The touch sensing chip TSC may be a Chip on Glass (COG)chip which is not disposed on the flexible printed circuit FPC1, but onthe first substrate SUB1.

The driver chip DRC and the touch sensing chip TSC are electricallyconnected to each other by means of the timing pulse, and the like andcooperate with respect to the operation timing. The driver chip DRC andthe touch sensing chip TSC may not be constituted as different ICs, butas the same IC. In this case, the single IC may be disposed on the firstsubstrate SUB1 or the flexible printed circuit FPC1. The driver chip DRCmay also be disposed not on the first substrate SUB1, but on theflexible printed circuit FPC1.

A backlight unit BL serving as an illumination device which illuminatesthe display panel PNL is provided on the back side of the firstsubstrate SUB1 (i.e., the back surface side of the display panel PNL).The host device HOST is connected to the backlight unit BL via aflexible printed circuit FPC2. Various types of backlight units can beemployed as the backlight unit BL. For example, a light-emitting diode(LED), a cold-cathode tube (CCFL) and the like, can be used as the lightsource. An illumination device using a light guide disposed on the backsurface side of the display panel PNL and an LED or a cold-cathode tubedisposed on its side surface side can be employed as the backlight unitBL. An illumination device using a spot light source in which lightemitting elements are aligned in plane on the back surface side of thedisplay panel PNL can also be employed as the backlight unit BL. Notonly the backlight, but a front light disposed on the display surfaceside of the display panel PNL can be used as the illumination device. Ifthe display device is a reflective display device or if the displaypanel PNL employs organic EL, the illumination device may not beprovided. The display device includes a secondary battery, a powercircuit, and the like, though not illustrated in the drawing.

The example shown in FIG. 1 is a longitudinally elongated screen inwhich the length of the Y direction is larger than the length of the Xdirection and the X direction is set as the lateral direction, but maybe applied to a laterally elongated screen in which the length of the Xdirection is larger than the length of the Y direction.

[Circuit Configuration]

FIG. 2 is a plan view showing an example of the display device accordingto the embodiments. FIG. 3 is a cross-sectional view showing an exampleof several parts of the display area DA. FIG. 4 is a plan view showingan example of arrangement of the common electrodes. FIG. 5 is anequivalent circuit diagram showing an example of a pixel. To facilitateviewing, constituent members of the display panel PNL will be shown inFIG. 2 and FIG. 4 separately. To illustrate an example of a positionalrelationship between a scanning line GL and a signal line SL in athickness direction of the first substrate SUB1 in FIG. 3, a scanningline GL provided in a cross-section different from FIG. 3 will be showntogether for convenience of explanations.

As shown in FIG. 2, the driver chip DRC includes a signal line driver SDwhich drives the display panel PNL. The touch sensing chip TSC includesa sensor SE including a capacitive-type touch detection function. Thesensor SE includes a detection controller DCP (FIG. 4) which controlsthe touch detection operation and processes a signal output from adetection electrode Rx (shown in FIG. 4). A configuration of the sensorSE serving as the touch detection circuit and a detection method of thesensor SE will be explained later. The display device includes a controlmodule provided outside the display panel PNL or the like and thecontrol module is electrically connected to the display panel PNL via aflexible printed circuit FPC1, though not illustrated in the figure. Thedetection controller DCP may be disposed inside the driver chip DRC.

As shown in FIG. 3, the backlight unit BL is disposed on a back surfaceside of the first substrate SUB1. An optical element OD1 is providedbetween the backlight unit BL and the first substrate SUB1. The firstsubstrate SUB1 includes an insulating substrate 10, insulating films 11,12, 13, and 14, the common electrode CE (also called a detectionelectrode Rx), the pixel electrode PE, and a first alignment film ALLThe second substrate SUB2 includes a second alignment film AL2, anovercoat layer OCL, red, green, and blue color filters CFR, CFG, andCFB, a black matrix BM, an insulating substrate 20, and a conductivefilm CDF. A liquid crystal layer LQ serving as an electro-optical layeris disposed between the first substrate SUB1 and the second substrateSUB2. An optical element OD2 is disposed on a surface side of the secondsubstrate SUB2. The surface of the optical element OD2 is a touchdetection surface TDS or a display surface DS on which an image isdisplayed.

As shown in FIG. 4, the display panel PNL includes detection electrodesRx disposed in a two-dimensional array in the first direction X and thesecond direction Y in the display area DA. The sensor SE detectsvariation in the electrostatic capacitance of each of the detectionelectrodes Rx, though the details are explained later. Since thedetection electrodes Rx are provided inside the display panel PNL, theembodiments relate to an in-cell type display device equipped with thetouch detection function. An example of a planar shape of the detectionelectrode Rx is a square, but may be an octagon formed by slightlycutting corners of a square, a shape formed by rounding corners of asquare, or the like.

As shown in FIG. 2, the driver chip DRC is provided in a non-displayarea NDA outside the display area DA of the display panel PNL on thefirst substrate SUB1. The driver chip DRC includes a signal line driverSD which drives the liquid crystal layer LQ (shown in FIG. 3) serving asan electro-optical layer via wirings SCL and signal lines SL, and thelike. As shown in FIG. 5, the signal line driver SD supplies a videosignal Spic to the pixel electrode PE provided in the pixel PX via thewiring SCL and the signal line SL.

In the display area DA, m x n pixels PX are aligned in a two-dimensionalarray in the X direction and the Y direction. Each of m and n is anarbitrarily positive integer. The signal lines SL extending in the Ydirection are spaced apart from each other and aligned in the Xdirection. “m” signal lines SL1, SL2, . . . SLm (generically called SL)are aligned in order of SL1, SL2, . . . SLm, from one side to the otherside in the X direction. Ends of the signal lines SL drawn to thenon-display area NDA outside the display area DA and are electricallyconnected to the driver chip DRC via connection wirings SCL for signalserving as connection wirings (also called connection leads).

The signal lines SL and the wirings SCL are video signal lines fortransmitting video signals, but the signal lines SL and the wirings SCLcan be distinguished in the following manner. The lines disposed insidethe display area DA, of the signal transmission paths connected to thedriver chip DRC to supply the video signals to the pixels PX, are calledthe signal lines SL, and the lines outside the display area DA arecalled the wirings SCL. The signal lines SL extend linearly in the Ydirection, in parallel with one another. Since the wirings SCL are thelines for connecting the signal lines SL and the driver chip DRC, thewirings SCL include bent portions having an entirely fan shape, betweenthe signal lines SL and the driver chip DRC.

The signal lines SL and the driver chip DRC may be connected directlyvia the wirings SCL or the other circuit may be disposed between thesignal lines SL and the driver chip DRC. For example, an RGB selectswitch for selecting a red video signal, a green video signal or a bluevideo signal may be interposed between the signal lines SL and thedriver chip DRC. The RGB select switch is, for example, a multiplexercircuit, which inputs signals formed by multiplexing the red videosignal, the green video signal, and the blue video signal andselectively outputs the input video signals to signal lines SL for eachcolor. In this case, the number of wirings SCL which connect the RGBselect switch and the driver chip DRC is smaller than the number ofsignal lines SL.

A scanning line driver GD serving as a scanning signal output circuitfor sequentially outputting scanning signals to the scanning lines GL isprovided in the non-display area NDA on the first substrate SUB1. Thedriver chip DRC is connected to the scanning line driver GD via a wiringW1 to supply control signals such as a clock signal and an enable signalto the scanning line driver GD. The scanning line GL extending in the Xdirection are spaced apart from each other and aligned in the Ydirection. “n” scanning lines GL1, GL2, . . . GLn (generically calledGL) are aligned in order of GL1, GL2, . . . GLn, from one side to theother side in the Y direction. Ends of the scanning lines GL are drawnto the non-display area NDA outside the display area DA and connected tothe scanning line driver GD. The scanning lines GL intersect the signallines SL.

The scanning line driver GD may include, for example, shift registercircuits (not shown) and a switch (also called a switching element)connected to the shift register circuit to select an electric potentialsupplied to the scanning line GL, based on the control signals. FIG. 2shows an example in which the scanning line driver GD is disposed in oneside in the X direction while a scanning line drive circuit is notdisposed in the other side, but the layout of the scanning line driverGD can be variously modified. For example, the scanning line driver GDmay be disposed on each of the sides in the X direction and the displayarea DA may be disposed between two scanning line drive circuits GD. Abuffer circuit for shaping waveforms of the control signals may beconnected between the driver chip DRC and the scanning line driver GD.

As shown in FIG. 4, the common electrodes CE are aligned in atwo-dimensional array in the X direction and the Y direction. Commonlines CML are connected to the common electrodes CE, respectively. Thecommon electrodes CE are connected to a switch circuit group SWG via thecommon lines CML. A common electrode driver CD (also called commonpotential circuit) which drives the common electrodes CE during theimage display is disposed on the flexible printed circuit FPC1 and iselectrically connected to the common electrodes CE via a commonpotential supply line VCDL, the switch circuit group SWG, and the commonlines CML.

In the embodiments, the common electrodes CE serve as the detectionelectrodes Rx for self-capacitive touch detection. For this reason, thecommon lines CML also has a function of lines for detected signaltransmission for transmitting the signals detected by the detectionelectrodes Rx to the sensor SE.

Since the self-capacitive touch detection is executed by using thedetection electrodes Rx, the common lines CML also has a function of thelines for signal transmission for inputting drive waveforms serving aswrite signals to the detection electrodes Rx, though explained later indetail.

The number of common electrodes CE may be equal to the number of pixelsPX shown in FIG. 2 or may be smaller than the number of pixels PX. Ifthe number of common electrodes CE which operate as the detectionelectrodes Rx is equal to the number of pixels PX, the resolution of thetouch detection becomes substantially the same as the resolution of thedisplay image. If the number of common electrodes CE is smaller than thenumber of pixels PX, the resolution of the touch detection is lower thanthe resolution of the display image but the number of common lines CMLcan be reduced. In general, the resolution of the display image is highas compared with the resolution of the touch detection. Therefore, thenumber of common electrodes CE may be smaller than the number of pixelsPX. For example, a plane area of one detection electrode Rx is 4 mm² to36 mm², one detection electrode Rx overlaps several tens to severalhundreds of pixels PX.

The switch circuit group SWG connected to the common lines CML isdisposed outside the driver chip DRC, though explained later in detail.The switch circuit group SWG is disposed in the non-display area NDA onthe first substrate SUB1. A control pulse generator CPG is connected tothe switch circuit group SWG.

The control pulse generator CPG is a circuit which selectively turns onand off switches (explained later in detail) provided in the switchcircuit group SWG. The control pulse generator CPG is disposed outsidethe driver chip DRC, for example, in the non-display area NDA on thefirst substrate SUB1. If the control pulse generator CPG is disposedoutside the driver chip DRC, versatility of the driver chip DRC isincreased. The control pulse generator CPG may be disposed inside thedriver chip DRC. Details of the layout of the switch circuit group SWGconnecting each of the detection electrodes Rx to the sensor SE will beexplained later in detail with reference to FIG. 13 and the like. Thecontrol pulse generator CPG may be disposed inside the driver chip DRC.

The arrangement of the scanning line driver GD (FIG. 2) and the commonelectrode driver CD (FIG. 4) is not limited to the examples shown inFIG. 2 and FIG. 4. For example, either or both of the scanning linedriver GD and the common electrode driver CD may be disposed in thedriver chip DRC. The common electrode driver CD may be disposed on thefirst substrate SUB1 shown in FIG. 2. The common electrode driver CD maybe disposed in the non-display area NDA. The common electrode driver CDmay be disposed outside the display panel PNL and connected to thedisplay panel PNL via the flexible printed circuit FPC1.

As shown in FIG. 5, each of the pixels PX includes the pixel switch PSWand the pixel electrode PE. The pixels PX may share one common electrodeCE. The pixel switch PSW includes, for example, a thin-film transistor(TFT). The pixel switch PSW is electrically connected to the scanningline GL and the signal line SL. A semiconductor layer of the pixelswitch PSW is formed of, for example, polycrystalline silicon(poly-silicon) but may be formed of amorphous silicon.

The pixel electrode PE is electrically connected to the pixel switchPSW. The pixel electrode PE is opposed to the common electrode CE viathe insulating film. The liquid crystal layer LQ is disposed between thepixel electrode PE and the common electrode CE. A storage capacitor CSis formed by the common electrode CE, an insulating film and the pixelelectrode PE.

An electric field is formed between the pixel electrode PE and thecommon electrode CE, based on the drive signal applied to eachelectrode, during the display period (shown in FIG. 15) in which adisplay image is formed based on the video signals. Liquid crystalmolecules contained in the liquid crystal layer LQ serving as theelectro-optical layer are driven by the electric field formed betweenthe pixel electrode PE and the common electrode CE. In the displaydevice using the lateral electric field mode, the pixel electrodes PEand the common electrodes CE are disposed on the first substrate SUB1 asshown in FIG. 3. The liquid crystal molecules contained in the liquidcrystal layer LQ are rotated by using the electric field formed betweenthe pixel electrode PE and the common electrode CE (for example, theelectric field approximately parallel to the main surface of thesubstrate, of the fringe field).

During the display period, each of the pixel electrode PE and the commonelectrode CE operates as the drive electrode which drives the liquidcrystal layer LQ serving as the electro-optical layer. The pixelelectrode PE is also called a first drive electrode which drives theelectro-optical layer. The common electrode CE is also called a seconddrive electrode which drives the electro-optical layer. As explainedabove, since the common electrode CE serves as the detection electrodeRx for the self-capacitive touch detection, the detection electrode Rxis also called the second drive electrode which drives theelectro-optical layer. In the following explanations, the detectionelectrode Rx is synonymous with the common electrodes CE or the driveelectrode which drives the electro-optical layer unless explainedespecially.

As shown in FIG. 3, the first substrate SUB1 and the second substrateSUB2 are bonded to each other while spaced apart in a certain distance.The liquid crystal layer LQ is sealed between the first substrate SUB1and the second substrate SUB2. The first substrate SUB1 includes theinsulating substrate 10 having a light transmitting property, such as aglass substrate or a resin substrate. The first substrate SUB1 includesconductive patterns on the side of the insulating substrate 10 which isopposed to the second substrate SUB2. The conductor patterns include thescanning lines GL, the signal lines SL, common lines CML, the commonelectrodes CE, and the pixel electrodes PE. The insulating films areintervened between the conductor patterns. The insulating films disposedbetween the adjacent conductor patterns to insulate the conductorpatterns from each other include the insulating films 11, 12, 13, 14,and the alignment film AL1. One scanning line GL, one common electrodeCE, and one common line CML are shown in FIG. 3.

The above-explained conductor patterns are formed on deposited wiringlayers, respectively. The common electrode CE and the pixel electrodesPE are formed in different layers. Three wiring layers WL1, WL2, and WL3are disposed under the layer in which the common electrode CE is formed.The scanning line GL is mainly formed in the first wiring layer WL1provided on the side closest to the insulating film 10, of three wiringlayers formed on the insulating substrate 10. The conductor patternformed in the wiring layer WL1 is composed of, for example, a metal suchas chromium (Cr), titanium (Ti) or molybdenum (Mo) or their alloys.

The insulating film 11 is formed on the wiring layer WL1 and theinsulating substrate 10. The insulating film 11 includes a transparentinsulating film formed of, for example, silicon nitride or siliconoxide. The scanning line GL, the gate electrode of the pixel switch, thesemiconductor layer, and the like are disposed between the insulatingsubstrate 10 and the insulating substrate 11.

The second wiring layer WL2 is formed on the insulating film 11. Thesignal line SL is mainly formed in the wiring layer WL2. The conductorpattern formed in the wiring layer WL2 includes, for example, a metalfilm of a multi-layer structure formed by sandwiching aluminum (Al)between molybdenum (Mo), titanium (Ti) and the like. The material of thewiring layer WL2 may be lower in specific resistivity than the materialof the wiring layer WL1. Source electrodes, drain electrodes and thelike of the pixel switches are also formed on the insulating film 11.The insulating film 12 is disposed on each of the signal lines SL andthe insulating film 11. The signal lines SL extend in the X direction.The insulating film 12 includes, for example, acrylic photosensitiveresin.

The third layer, i.e., the third wiring layer WL3 is formed on theinsulating film 12. The common line CML is mainly formed in the wiringlayer WL3. The conductor pattern formed in the wiring layer WL3includes, for example, a metal film of a multi-layer structure formed bysandwiching aluminum (Al) between molybdenum (Mo), titanium (Ti) and thelike, similarly to the wiring layer WL2. The common line CML extends inthe Y direction. The insulating film 13 is formed on each of the commonline CML and the insulating film 12. The insulating film 13 is formedof, for example, acrylic photosensitive resin.

The common electrodes CE are formed on the insulating film 13. Thecommon electrodes CE serve as the detection electrodes Rx for touchdetection. The common electrodes CE may be formed of a transparentconductive material such as indium tin oxide (ITO) or indium zinc oxide(IZO). If the display device is a display device of the longitudinalelectric field mode (for example, TN mode or VA mode), the commonelectrodes CE may be formed on the second substrate SUB2. The insulatingfilm 13 is intervened between the common electrodes CE and the commonlines CML. As shown in FIG. 4, however, parts of the common lines CMLand parts of the common electrodes CE are electrically connected to eachother. If the display device is a reflective display device usingreflection of external light, the common electrodes CE may be formed ofa metal material.

The insulating film 14 is formed on the common electrodes CE. The pixelelectrodes PE are formed on the insulating film 14. Each of the pixelelectrodes PE is disposed between two adjacent signal lines SL andopposed to the common electrode CE. The pixel electrode PE is formed of,for example, a transparent conductive material or metal material such asITO or IZO. The alignment film AL1 covers the pixel electrodes PE andthe insulating film 14.

The second substrate SUB2 includes the insulating substrate 20 having alight transmitting property, such as a glass substrate or a resinsubstrate. The second substrate SUB2 includes the black matrix BM whichis a light-shielding layer, color filters CFR, CFG, and CFB, overcoatlayer OCL, alignment film AL2, and conductive film CDF, on a side of theinsulating substrate 20 which is opposed to the first substrate SUB1.

The black matrix BM is a light-shielding area formed on a surface of theinsulating substrate 20 on the first substrate SUB1 side to partitioneach pixel. Each of the red, green, and blue color filters CFR, CFG, andCFB is formed on the surface of the insulating substrate 20 on the firstsubstrate SUB1 side. When the display surface of the display panel PNLis seen from a direction perpendicular to the surface, each of the colorfilters CFR, CFG, and CFB partially overlaps the black matrix BM. Thered color filter CFR is a color filter which allows light of awavelength of a red component to be transmitted, the green color filterCFG is a color filter which allows light of a wavelength of a greencomponent to be transmitted, and the blue color filter CFB is a colorfilter which allows light of a wavelength of a blue component to betransmitted. The overcoat layer OCL covers the color filters CFR, CFG,and CFB. The overcoat layer OCL is formed of a transparent resinmaterial. The alignment film AL2 covers the overcoat layer OCL.

The common electrodes CE are formed of a transparent material such asITO but its resistance value is high. To lower the resistance value ofthe common electrodes CE, a metal line 3M called a third metal line isprovided in an area shielded from light by the black matrix BM of thewiring layer WL3.

The conductive film CDF is disposed on a plane of the side opposite tothe surface opposed to the liquid crystal layer LQ, of planes of theinsulating substrate 20. The conductive film CDF is formed of, forexample, a transparent conductive material such as ITO or IZO. Theconductive film CDF functions as a shield layer for suppressing aninfluence of electromagnetic waves from the outside to the liquidcrystal layer LQ and the like. If the mode of driving the liquid crystallayer LQ is the longitudinal electric field mode such as TN mode or VAmode, the electrodes are provided on the second substrate SUB2 and alsofunction as shield layers, and arrangement of the conductive film CDFcan be omitted. If the touch detection is executed in themutual-capacitive mode, the conductive films CDF subjected to patterningare formed on the insulating substrate 20. The conductive films CDF maybe used as the detection electrodes for touch detection.

The display panel PNL includes optical elements OD1 and OD2. The opticalelement OD1 is interposed between the insulating substrate 10 and thebacklight unit BL. The optical element OD2 is disposed above theinsulating substrate 20, i.e., the insulating substrate 20 is arrangedbetween the optical element OD2 and the first substrate SUB1. Each ofthe optical element OD1 and the optical element OD2 includes at least apolarizer and may include a phase difference film as needed.

[Touch Detection]

A method of detecting a position of an input object such as a finger ora stylus, i.e., an input position by the display panel PNL using thedetection electrodes Rx will be explained. The display panel PNL candetermine the input position information, based on the variation in theelectrostatic capacitance detected by the detection electrodes Rx in theself-capacitive sensing mode. A finger touching or approaching the touchdetection surface TDS (FIG. 3) of the display panel PNL can be therebydetected. The touch detection surface TDS is one of surfaces of theoptical element OD2, on a side opposite to the second substrate SUB2.

A principle and a method of the touch detection in the self-capacitivesensing mode will be hereinafter explained. However, the display panelPNL may determine the input position information, based on the variationin the electrostatic capacitance detected by the detection electrodes Rxin the mutual-capacitive mode. The detection in the self-capacitivesensing mode and the detection in the mutual-capacitive mode may beexecuted alternately. If the display device includes detectionelectrodes in the self-capacitive sensing mode and detection electrodesin the mutual-capacitive mode independently, the self-capacitive sensingmode and the mutual-capacitive mode may be executed simultaneously. Thetouch detection in the self-capacitive sensing mode is executed based onthe variation in signals output from the detection electrodes Rx, byinputting the drive signals to the detection electrodes Rx.

A principle of a touch detection method in the self-capacitive sensingmode will be explained. The self-capacitive sensing mode usescapacitance Cx1 which the detection electrodes Rx have and capacitanceCx2 generated by a finger or the like of the user who touches thedetection electrodes Rx. FIG. 6 to FIG. 9 are explanatory viewsschematically showing a circuit operation of the touch detection in theself-capacitive sensing mode.

FIG. 6 and FIG. 7 show a state in which the user's finger does not touchthe touch detection surface of the display panel PNL. In this state,electrostatic capacitive coupling does not occur between the detectionelectrode Rx and the finger. FIG. 6 shows a state in which the detectionelectrode Rx is connected to power source Vdd by a switch SW1. FIG. 7shows a state in which the detection electrode Rx is disconnected fromthe power source Vdd and connected to capacitance Cy1 serving as acapacitor by the switch SW1.

In the state shown in FIG. 6, electric charges Q1 flow from the powersource Vdd to capacitance Cx1, and the capacitance Cx1 is charged. Inthe state shown in FIG. 7, electric charges Q2 flow from the capacitanceCx1 to the capacitance Cy1, and the capacitance Cx1 is discharged.Charging the capacitance Cx1 indicates writing the write signal to thedetection electrode Rx. Discharging the capacitance Cx1 indicatesreading the read signal indicating the variation in the electrostaticcapacitance which has occurred in the detection electrode Rx.

FIG. 8 and FIG. 9 show a state in which the user's finger touches thetouch detection surface TDS of the display panel PNL. In this state,electrostatic capacitive coupling occurs between the detection electrodeRx and the finger. FIG. 8 shows a state in which the detection electrodeRx is connected to the power source Vdd by the switch SW1. FIG. 9 showsa state in which the detection electrode Rx is disconnected from thepower source Vdd and connected to the capacitance Cy1 by the switch SW1.

In the state shown in FIG. 8, electric charges Q3 flow from the powersource Vdd to the capacitance Cx1, and the capacitance Cx1 is charged.In the state shown in FIG. 9, electric charges Q4 flow from thecapacitance Cx1 to the capacitance Cy1, and the capacitance Cx1 isdischarged.

Time dependence of the voltage charged to the capacitance Cy1 at thedischarge of the capacitance Cx1 shown in FIG. 7 is different from thetime dependence of the voltage charged to the capacitance Cy1 at thedischarge of the capacitance Cx1 shown in FIG. 9 since capacitance Cx2exists in the state shown in FIG. 9. Therefore, in the self-capacitivesensing mode, the input position information (for example, operationinput) is determined by using the feature that the time dependence ofthe voltage of the capacitance Cy1 is varied in accordance with thecapacitance Cx2.

An example of a circuit which implements the self-capacitive sensingmode will be explained. FIG. 10 shows an example of a circuitimplementing the self-capacitive sensing mode. FIG. 11 shows examples oftime dependence of the voltage of the detection electrode Rx, analternating square wave output from the power source Vdd, and thevoltage which is an output of a detector DET. In FIG. 10, thecapacitance of the detection electrode Rx is called the capacitance Cx1.The switch circuit group SWG shown in FIG. 4 is connected in the middleof a detection signal line DSL between the sensor SE (DCP) and thedetection electrode Rx.

As shown in FIG. 10, electric connection of the detection electrode Rxto the power source Vdd is turned on and off by turning on and off theswitch SW1. Electric connection of the detection electrode Rx to thedetector DET (for example, a voltage detector) is turned on and off byturning on and off a switch SW2. The detector DET is an integratorcircuit, which includes, for example, an operational amplifier OPd, acapacitance Cd, and a switch SW3. A non-inverting input terminal of theoperational amplifier OPd is connected to the detection electrode Rx viathe switch SW2. A reference signal Vref is input to an inverting inputterminal of the operational amplifier OPd.

As shown in FIG. 11, the power source Vdd outputs an alternating squarewave Sg having a wave height of a voltage Vdr by setting a timedifference between time T01 and time T02 as a cycle. The alternatingsquare wave Sg has, for example, a frequency from several kHz to severalhundreds of kHz. The detector DET converts the variation in the currentaccording to the alternating square wave Sg into variation in voltage(i.e., waveform Vdet0 or waveform Vdet1). The waveform Vdet0 andwaveform Vdet1 are generically called waveforms Vdet.

As explained with reference to FIG. 10, electric connection of thedetection electrode Rx to the power source Vdd and the detector DET canbe changed by turning on and off the switch SW1 and the switch SW2. InFIG. 11, the alternating square wave Sg rises by voltage Vdr at timeT01. At time T01, the switch SW1 is turned on while the switch SW2 isturned off. For this reason, voltage Vx of the detection electrode Rxalso rises by the voltage Vdr at time T01. The switch SW1 is turned offbefore time T11. At this time, if both of the switch SW1 and the switchSW2 are turned off, the detection electrode Rx is in a state of floatingelectrically, i.e., a floating state. However, the voltage Vx of thedetection electrode Rx is a voltage at which rise of the voltage Vdr ismaintained, by the capacitance Cx1 (FIG. 6) of the detection electrodeRx or capacitance Cx1+Cx2 obtained by adding the capacitance Cx2 (FIG.8) added by touch of a finger or the like to the capacitance Cx1 of thedetection electrode Rx. Furthermore, the switch SW3 is turned on beforetime T11 and then the switch SW3 is turned off before time T11. VoltageVdet which is the output of the detector DET is reset by this operation.After executing the reset operation, the voltage Vdet of the detectorDET becomes approximately equal to the voltage of the reference signalVref.

Then the switch SW2 is turned on at time T11. The voltage input to thenon-inverting input terminal of the detector DET becomes equal to thevoltage Vx of the detection electrode Rx. After that, the voltage of aninverting input terminal of the detector DET is lowered to a valueapproximately equal to the reference signal Vref at a response speedaccording to a time constant resulting from the capacitance Cx1 of thedetection electrode Rx (or the above capacitances Cx1+Cx2) and thecapacitance Cd included in the detector DET. Since the electric chargesstored in the capacitance Cx1 of the detection electrode Rx (or thecapacitances Cx1+Cx2) move to the capacitance Cd included in thedetector DET, the voltage Vdet of the detector DET rises. The voltageVdet becomes a voltage having waveform Vdet0 represented by a solid linewhen an object such as a finger does not touch the detection electrodeRx. Vdet0=Cx1×Vdr/Cd. The voltage Vdet becomes a voltage having waveformVdet1 represented by a broken line when an object such as a fingertouches and the capacitance generated by an influence of the object isadded. Vdet1=(Cx1+Cx2)×Vdr/Cd

Then, the switch SW2 is turned off while the switch SW1 and the switchSW3 are turned on at time T31 after the electric charges of thecapacitance Cx1 of the detection electrode Rx (or the capacitancesCx1+Cx2) have sufficiently moved to the capacitance Cd. By thisoperation, the voltage of the detection electrode Rx becomes equal to alow level of the alternating square wave Sg, i.e., a relatively lowervoltage level of the square wave. The voltage which is the output fromthe detector DET is reset by the reset operation of turning off theswitch SW2 and turning on the switch SW3. The switch SW1 may be turnedon at any timing before time T02 after turning off the switch SW2. Inaddition, the detector DET may be reset at any timing before time T12after turning off the switch SW2.

In a period of executing the touch detection, the operations explainedwith reference to FIG. 6 to FIG. 11 are repeated in a predeterminedfrequency (for example, approximately, several kHz to several hundredsof kHz) for each of the detection electrodes Rx shown in FIG. 4.Presence of the object (touch) which has touched the touch detectionsurface from the outside can be measured, based on absolute value |ΔV|of a difference between the waveform Vdet0 and the waveform Vdet1.

The operation principles of the self-capacitive sensing mode and thetypical example of the circuit implementing the self-capacitive sensingmode have been explained above. However, the method of implementing theself-capacitive sensing mode can be variously modified. For example,touch detection of the following modified example may be executedinstead of the self-capacitive touch detection or in addition to theabove-explained self capacitive touch detection. If the object such as afinger does not touch the touch detection surface, the waveform of thevoltage Vx of the detection electrode Rx becomes voltage Vx0 representedby a solid line of FIG. 11. When the object such as a finger touches thetouch detection surface and the capacitance Cx2 resulting from aninfluence of the object is added, the waveform of the voltage Vx of thedetection electrode Rx becomes a voltage having waveform Vx1 representedby a broken line of FIG. 11. For this reason, if periods of time inwhich the waveform Vx0 and the waveform Vx1 lower to a threshold voltageVth exemplified by a two-dot-chained line in FIG. 11 are measured andcompared, presence of the object (touch) which has touched the touchdetection surface from the outside can be determined.

[CDM Drive]

The embodiments may employ a code division multiplexing (CDM) drivemethod, as the method of driving the detection electrode for touchdetection. The CDM drive method is capable of executing the touchdetection in a short time by enhancing the detection sensitivity andimproving the touch detection accuracy. In the CDM drive, apredetermined number of detection electrodes in each row or each columnare classified into groups, the detection electrodes are simultaneouslydriven and detected in the group, and simultaneous drive is executedseveral times while changing combination of the simultaneously drivendetection electrodes. By operating the signals obtained by thesimultaneous drive, an amplified value of the detected value of eachdetection signal can be obtained.

FIG. 12 shows an operation of the switch circuit group SWG for CDM drive(schematically shown in FIG. 4). Ends of drive signal lines TSpL1,TSpL2, . . . of the respective rows are connected to the touch sensingchip TSC (sensor SE), and the other ends of the drive signal linesTSpL1, TSpL2, . . . of the respective rows are connected to first inputends of the switch circuits SW of the respective rows. The switchcircuits SW are connected to the detection elements Rx of the respectiverows. An end of a guard signal line TSnL common to all of the detectionelectrodes Rx is connected to the touch sensing chip TSC (sensor SE),and the other end of the guard signal line TSnL is connected to secondinput ends of all the switch circuits SW connected to all the detectionelements Rx. A common potential supply line VDCL has an end connected tothe common electrode driver CD and the other end connected to thirdinput ends of all the switch circuits SW connected to all the detectionelectrodes Rx. The switch circuits SW in each column are controlled bydrive signals from the control pulse generator CPG In FIG. 12, eachswitch circuit SW is illustrated under the detection element Rx of eachrow for convenience of explanation but, in fact, all the switch circuitsSW are provided under the entire array of the detection elements Rx, inthe non-display area NDA, as the switch circuit group SWG. Each of thedrive signal lines TSpL1, TSpL2, . . . corresponds to the detectionsignal line DSL shown in FIG. 10.

The drive signals are supplied via the drive signal lines TSpL1, TSpL2,. . . to the detection electrodes Rx selected in accordance withselection of the switch circuits SW. If the drive signals are suppliedto several detection electrodes, in the array of the detectionelectrodes Rx, a potential difference may occur between detectionelectrodes which are supplied with the drive signals and detectionelectrodes which are not supplied with the drive signals, and parasiticcapacitance may be thereby generated. In the embodiments, signals havingthe same waveform as the drive signals are supplied to unselecteddetection electrodes which are not supplied with the drive signals.Thereby, generation of the parasitic capacitance is suppressed. Thesignals having the same waveform as the drive signals input to theunselected detection electrodes are called guard signals. The guardsignals are common to all the detection electrodes.

In the display period, the switch circuits SW are controlled to supplyto all the detection electrodes Rx a constant DC voltage supplied fromthe common electrode driver CD via the common potential supply lineVDCL. In the touch detection period, the switch circuits SW arecontrolled to supply to the selected detection electrodes the drivesignals supplied from the sensor SE via the drive signal lines TSpL1,TSpL2, . . . , and to supply to the unselected detection electrodes theguard signals supplied from the sensor SE via the guard signal lineTSnL.

FIG. 13 is a circuit diagram showing the switch circuits SW of one rowin the switch circuit group SWG shown in FIG. 4. The detection elementarray is assumed to include the detection elements of six columns forconvenience of explanations. The switch circuit SW of each column j iscomposed of three switches SWdj, SWpj, and SWnj. The switches areillustrated as on/off switches but are formed of TFTs for convenience ofexplanations.

A first terminal of the switch SWdj is connected to the common potentialsupply line VDCL. A first terminal of the switch SWpj is connected tothe drive signal line TSpL1. A first terminal of the switch SWnj isconnected to the guard signal line TSnL. Second terminals of theswitches SWdj, SWpj, and SWnj are connected commonly and commonconnections are connected to the detection electrodes Rxj via the commonlines CML.

The switches SWdj of all the columns are turned off in the touchdetection period and turned on in the display period, by the controlsignals supplied from the control pulse generator CPG via the controlsignal line CSdL. As a result, the common potential is supplied from thecommon potential supply line VDCL to the detection electrodes Rx in thedisplay period. The

switches SWpj and SWnj are driven complementarily for each column by thecontrol signals supplied from the control pulse generator CPG via thecontrol signal lines CSpL and CSnL (one of the switches is turned onwhen the other is turned off). The switches SWpj and SWnj are turned offin the display period, and sequentially turned on for each column in thetouch detection period. As a result, the drive signals or the guardsignals are supplied to the detection electrodes Rx in the touchdetection period. The detection electrodes of the other rows are alsoconnected to the switch circuits SW of each row similarly to FIG. 13,and the switch circuits SW of each row are connected to the sensor SEfor each row.

The principle of CDM will be explained with reference to FIG. 14.Driving the detection electrodes Rx of four rows and six columns by“CDM3” will be explained for convenience of explanations. “CDM3” is adriving method of executing simultaneous drive of two detectionelectrodes three times while recognizing three detection electrodes asone group. Each drive is called scan. Driving one group is completed bythree scans. In the CDM drive, the detection electrodes of the samecolumn of all rows are driven simultaneously. Driving the detectionelectrodes one after another is also called “CDM1”.

In the first scan (scan 1), the detection electrodes Rx11 to Rx41 andRx12 to Rx42 of the first and second columns are connected to the drivesignal lines TSpL1 to TSpL4, and the other detection electrodes areconnected to the guard signal line TSnL. For this reason, in the firstscan, the sensor SE detects, for each row i, a total of detection valuesof the detection electrodes Rxi1 and Rxi2 of the first and secondcolumns. In the second scan (scan 2), the detection electrodes Rx12 toRx42 and Rx13 to Rx43 of the second and third columns are connected tothe drive signal lines TSpL1 to TSpL4, and the other detectionelectrodes are connected to the guard signal line TSnL. For this reason,in the second scan, the sensor SE detects, for each row i, a total ofdetection values of the detection electrodes Rxi2 and Rxi3 of the secondand third columns. In the third scan (scan 3), the detection electrodesRx11 to Rx41 and Rx13 to Rx43 of the first and third columns areconnected to the drive signal lines TSpL1 to TSpL4, and the otherdetection electrodes are connected to the guard signal line TSnL. Forthis reason, in the third scan, the sensor SE detects, for each row i, atotal of detection values of the detection electrodes Rxi1 and Rxi3 ofthe first and third columns. The detection electrodes of each of thefirst, second, and third rows are driven two times in three scans.

Next, scan of the detection electrodes of the fourth to sixth columns isexecuted similarly to scan of the detection electrodes of the first tothird columns. In the fourth scan (scan 4), the detection electrodesRx14 to Rx44 and Rx15 to Rx45 of the fourth and fifth columns areconnected to the drive signal lines TSpL1 to TSpL4, and the otherdetection electrodes are connected to the guard signal line TSnL. Forthis reason, in the fourth scan, the sensor SE detects, for each row i,a total of detection values of the detection electrodes Rxi4 and Rxi5 ofthe fourth and fifth columns. In the fifth scan (scan 5), the detectionelectrodes Rx15 to Rx45 and Rx16 to Rx46 of the fifth and sixth columnsare connected to the drive signal lines TSpL1 to TSpL4, and the otherdetection electrodes are connected to the guard signal line TSnL. Forthis reason, in the fifth scan (scan 5), the sensor SE detects, for eachrow i, a total of detection values of the detection electrodes Rxi5 andRxi6 of the fifth and sixth columns. In the sixth scan (scan 6), thedetection electrodes Rx14 to Rx44 and Rx16 to Rx46 of the fourth andsixth columns are connected to the drive signal lines TSpL1 to TSpL4,and the other detection electrodes are connected to the guard signalline TSnL. For this reason, in the sixth scan, the sensor SE detects,for each row i, a total of detection values of the detection electrodesRxi4 and Rxi6 of the fourth and sixth columns. The detection electrodesof each of the fourth, fifth, and sixth rows are driven two times inthree scans. If the detection electrodes Rx of the seventh or morecolumns are disposed, scan of the detection electrodes of three columnsis executed similarly to scan of the detection electrodes of the firstto third columns.

FIG. 15 is a timing chart showing turning on/off the switches forexplanation of the “CDM3” shown in FIG. 14. In the figure, the highlevel indicates turning on the switches while the low level indicatesturning off the switches. In other words, FIG. 15 is also a timing chartshowing control of the control pulse generator CPG which controls theswitches. The display device of the embodiments has a display operationperiod FLD for executing a display operation of forming the imagedisplayed on the display surface DS (see FIG. 3) and a touch detectionoperation period FLT for executing a touch detection operation ofdetecting touch of the object such as a finger on the touch detectionsurface TDS. The display operation period FLD is also called a displayperiod. The touch detection operation period FLT is also called adetection period. The display operation FLD and the touch detectionoperation FLT are repeated. For this reason, the display periods FLD andthe detection periods FLT are alternately repeated along the time axis(lateral direction) in the time chart shown in FIG. 15.

The switches SWd connected to the detection elements of all the rows andall the columns are turned off in the detection periods FLT and turnedon in the display periods FLD. The switches SWp and SWn connected to thedetection elements of all the rows and all the columns are turned off inthe display periods FLD. For this reason, the common potential issupplied from the common potential supply line VDCL to all the detectionelectrodes Rx via the switches SWd in the display periods FLD. In thedisplay periods FLD, the liquid crystal layer LQ (see FIG. 2) which isthe electro-optical layer is driven based on the video signals and thedisplay image is formed.

In the detection periods FLT, the switches SWp and SWn connected to thedetection elements of each row are turned on in every two columns andthe turned-on switches are sequentially changed as shown in FIG. 14.When the switches SWpj are turned on (or off), the switches SWnj areturned off (or on). If the detection electrodes Rx are arranged in sixcolumns, the first scan is repeated after the sixth scan. The sensor SEoutputs a drive signal DSp shaped in a high frequency pulse to the drivesignal lines TSpL and a guard signal DSn having the same waveform as thedrive signal to the guard signal line TSnL in the detection period FLT.For this reason, the drive signals DSp are supplied to the detectionelectrodes Rx of two columns selected by two turned-on switches SWp, andthe guard signals DSn are supplied to the detection electrodes Rx of theother columns. The touch detection operation in the self-capacitivesensing mode explained with reference to FIG. 6 to FIG. 11 is therebyexecuted. The sensor SE detects a total of the detection values of thedetection electrodes Rx of each row and two columns, via the drivesignal lines TSpL serving as the detection signal lines DSL, and thedetection value of each detection electrode Rx is obtained from thetotal detection value by the following operation.

In the touch detection period, driving the detection electrodes Rx ofany two columns, of the detection electrodes Rx of three columnsconstituting one group of each row, by the drive signals DSp via thedrive signal lines TSpL indicates that the drive signals DSp are codedby a code pattern (1 indicates the drive signal DSp and 0 indicates theguard signal DSn). The code pattern corresponds to turning on and offthe switches SWp.

If the detection values of the detection electrodes Rx11, Rx12, and Rx13are represented by s11, s12, and s13, total detection values Sc1, Sc2,and Sc3 of the detection electrodes Rx11, Rx12, and Rx13 detected byeach scan are represented by Equation 1.

$\begin{matrix}{\begin{bmatrix}{{Sc}\; 1} \\{Sc2} \\{Sc3}\end{bmatrix} = {\begin{bmatrix}1 & 1 & 0 \\0 & 1 & 1 \\1 & 0 & 1\end{bmatrix}\begin{bmatrix}{s\; 11} \\{s\; 12} \\{s\; 13}\end{bmatrix}}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

Since the drive signal DSp is coded, values which are double thedetection values s11, s12, and s13 of the respective detectionelectrodes can be obtained by operating an inverse matrix of the totaldetection values Sc1, Sc2, and Sc3 of the detection values of thedetection electrodes Rx in the coding pattern of the drive signal DSp.

$\begin{matrix}{{\begin{bmatrix}1 & {- 1} & 1 \\1 & 1 & {- 1} \\{- 1} & 1 & 1\end{bmatrix}\begin{bmatrix}{{Sc}\; 1} \\{Sc2} \\{Sc3}\end{bmatrix}} = \begin{bmatrix}{2 \times s\; 11} \\{2 \times s\; 12} \\{2 \times s\; 13}\end{bmatrix}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$

The detection value of each detection electrode Rx can be obtained fromthe total detection values of two detection electrodes Rx by executingoperation of Equation 2 by the sensor SE, and the obtained detectionvalue is double the actual detection value. Thus, the amplitude of thedetection signal can be amplifies and the detection sensitivity can beincreased.

It is assumed that, for example, the detection value of the touchportion is 1.2, the detection value of the non-touch portion is 1.0, andthe detection electrode Rx12 is the touch portion. Since detection values12 of the detection electrode Rx12 is 1.2 and detection values s11 ands13 of the other detection electrodes Rx11 and Rx13 are 1.0, totaldetection values Sc1, Sc2, and Sc3 of the respective first scan, secondscan, and third scan are as follows.

Sc1=1×1.0+1×1.2+0×1.0=2.2

Sc2=0×1.0+1×1.2+0×1.0=2.2

Sc3=1×1.0+0×1.2+1×1.0=2.0

If an inverse matrix of the code pattern is operated, the signals of thedetectors Rx11, Rx12, and Rx13 are as follows.

$\begin{matrix}{{{Signal}\mspace{14mu} {of}\mspace{14mu} {Detector}\mspace{14mu} {Rx}\; 11} = {{1 \times {Sc}\; 1} + {\left( {- 1} \right) \times Sc2} + {1 \times {Sc}\; 3}}} \\{= {2.2 - 2.2 + 2.0}} \\{= 2.0}\end{matrix}$ $\begin{matrix}{{{Signal}\mspace{14mu} {of}\mspace{14mu} {Detector}\mspace{14mu} {Rx}\; 12} = {{1 \times {Sc}\; 1} + {1 \times S\; c\; 2} + {\left( {- 1} \right) \times {Sc}\; 3}}} \\{= {2.2 + 2.2 - 2.0}} \\{= 2.4}\end{matrix}$ $\begin{matrix}{{{Signal}\mspace{14mu} {of}\mspace{14mu} {Detector}\mspace{14mu} {Rx}\; 13} = {{\left( {- 1} \right) \times {Sc}\; 1} + {1 \times {Sc}\; 2} + {1 \times {Sc}\; 3}}} \\{= {{- 2.2} + 2.2 + 2.0}} \\{= 2.0}\end{matrix}$

Thus, the signals of the detectors Rx11, Rx12, and Rx13 become doublethe detection values. Since the signal of the detection electrode Rx12is higher than the signals of the other detection electrodes, thedetection electrode Rx12 can be determined as the touch electrode. Afterthat, the detection values of the detection electrodes of three columnscan be obtained by three scans in the similar manner.

If the touch is detected on a certain detection electrode Rx,coordinates of the position of the detection electrode Rx by which thetouch has been detected on the touch detection surface (see FIG. 2) arecalculated and the coordinate data are output to an external circuitsuch as the host device. The external circuit changes the image in thedisplay area DA, based on the acquired coordinate data. Calculation ofthe position coordinates and output of the coordinate data may beexecuted by, for example, a circuit (for example, a data processingcircuit) included in the sensor SE. The data processing circuit may beformed on the substrate SUB1 or formed in the driver chip DRC. The dataprocessing circuit may be formed on the flexible printed circuit FPC1 ormay be formed at a location remote from the display panel PNL andconnected via the flexible printed circuit FPC1.

If the touch is not detected on any detection electrodes Rx, thecoordinate data are not output to the external circuit. Alternatively,the above data processing circuit may output to the external circuit asignal indicating that the touch is not detected on any detectionelectrodes Rx.

Not only CDM3, but CDM4, CDM5, . . . and the like can be employed. Forexample, in CDM4, four detection electrodes are determined as one groupand simultaneous drive of three detection electrodes is executed fourtimes. If the detection value of each detection electrode Rx is obtainedfrom the total detection values of three detection electrodes Rx, avalue which is four times as large as the actual detection value can beobtained. In CDM9, simultaneous drive of five detection electrodes isexecuted nine times. The number of simultaneously driven electrodes andthe number of times of simultaneous drive can be selected arbitrarily.The sensitivity is increased as the number of simultaneously drivenelectrodes is larger.

[Switch Circuit Group SWG]

As shown in FIG. 4, the detection electrode Rx array is disposed in thedisplay area DA, and the switch circuit group SWG is disposed in thenon-display area NDA. For this reason, as shown in FIG. 16, the distancebetween the detection electrodes Rx of each row and the switch circuitgroup SWG is different in each row. The common line CML connecting thedetection electrodes Rx remotest from the switch circuit group SWG, forexample, the detection electrodes Rx11 to Rx16 of the first row to theswitch circuit group SWG is the longest, and the common line CMLconnecting the detection electrodes Rx closest to the switch circuitgroup SWG, for example, the detection electrodes Rx41 to Rx46 of thefourth row to the switch circuit group SWG is the shortest. As theresistance of the common line is proportional to its length, theresistance between the switch circuit group SWG and the detectionelectrodes of each row is different in each row. For this reason,on-resistances of the TFTs constituting the switches SWd, SWp, and SWnincluded in the switch circuit group SWG do not need to be the same, butthe on-resistance of the TFTs connected to the remote detectionelectrodes Rx11 to Rx16 via the longer CML line needs to be small whilethe on-resistance of the TFTs connected to the closer detectionelectrodes Rx41 to Rx46 via the shorter CML line may be large. Theon-resistance of the TFT is inversely proportional to the channel width.For this reason, all the channel widths of TFTs 161, 162, 163, and 164connected to the detection electrodes of the first to fourth rows do notneed to be equal and may be different. The channel width of the TFT 161connected to the detection electrodes Rx11 to Rx16 of the first row maybe the largest, the channel widths of the TFT 162 and TFT 163 connectedto the detection electrodes of the second and third rows may becomesmaller, and the channel width of the TFT 164 connected to the detectionelectrodes Rx41 to Rx46 of the fourth row may be the smallest. FIG. 17Ashows an example of the TFT 164 connected to the detection electrodes ofthe fourth row. FIG. 17B shows an example of the TFT 161 connected tothe detection electrodes of the first row. A channel width W1 of the TFT164 along the gate line Ga is thus smaller than a channel width W2 ofthe TFT 161.

Thus, the channel width of the TFT connected to the detection electrodeRx which is the closest to the switch circuit group SWG, of the TFTsincluded in the switch circuit group SWG, can be made smaller than thechannel widths of the other TFTs. For this reason, an occupation area ofthe TFTs is reduced, free space is increased on the first substrateSUB1, and mounting the circuits and layout of wirings are facilitated.If the degree of freedom of the wiring is increased and the density ofwiring is reduced, the occurrence of the parasitic capacitance and theparasitic resistance can be suppressed.

[Wiring Example of Detection Electrodes Rx and Sensor SE]

As shown in FIG. 13, if the CDM drive is executed in the row direction,one drive signal line TSpL is connected to the detection electrodes Rxof all the columns of each row via the switches SWp. If the CDM drive isexecuted in the columnar direction, the connection shown in FIG. 18 andFIG. 20 can also be made.

FIG. 18 shows a modified example in which one drive signal line TSpL isconnected to the detection electrodes Rx of all the rows of each columnvia the switches SWp in the switch circuit group SWG. For example, thedrive signal TSpL1 is connected to the detection electrodes Rx11 to Rx41of the first column of all the rows via the switch circuit group SWG.The drive signal TSpL2 is connected to the detection electrodes Rx12 toRx42 of the second column of all the rows via the switch circuit groupSWG. FIG. 19 shows a wiring example corresponding to FIG. 13 forcomparison, i.e., a wiring example in which one drive signal line TSpLis connected to the detection electrodes Rx of all the columns of eachrow via the switch circuit group SWG. For example, the drive signalTSpL1 is connected to the detection electrodes Rx11 to Rx14 of all thecolumns of the first row via the switch circuit group SWG. In FIG. 18,the detection electrodes Rx connected to one drive signal line TSpL arearranged in the column direction (Y direction). In this case, in FIG.18, since each of the drive signal lines TSpL1, TSpL2, TSpL3, and TSpL4is merely connected to the drive electrodes of each column, in thenon-display area NDA lower than the switch circuit group SWG, thenon-display area NDA can be narrowed. In FIG. 19, since each of thedrive signal lines TSpL1, TSpL2, TSpL3, and TSpL4 is connected to thedrive electrodes of the first to fourth columns, in the non-display areaNDA lower than the switch circuit group SWG, the non-display area NDAcan hardly be narrowed.

Furthermore, in the configuration shown in FIG. 18, the resolution inthe row direction (X direction) can be increased, in what is calledbundle drive in which, by sequentially selecting the drive electrodes ineach predetermined number in time division and applying the drive signalDSp to the selected drive electrodes, the scan drive is executed to makethe scan pitch smaller than the full length of the predetermined numberof drive electrodes.

FIG. 20 shows a modified example in which one drive signal line TSpL isconnected to the detection electrodes Rx of plural rows of pluralcolumns, for example, 2×2, via the switch circuit group SWG. Forexample, the drive signal TSpL1 is connected to four detectionelectrodes Rx11, Rx12, Rx21, and Rx22 of two rows x two columns via theswitch circuit group SWG. In FIG. 20, the detection electrodes Rxconnected to one drive signal line TSpL are arrayed in the X and Ydirections. Is this configuration is what is called bundle drive, theresolution in the X and Y directions is uniform. For this reason, thisconfiguration can be applied to not only detection of complete touch,but detection of hover mode which detects a state of being remote in acertain distance.

[Example of Wiring Layout on First Substrate SUB1]

As shown in FIG. 2 and FIG. 4, the sensor SE is included in the touchsensing chip TSC which is the COF chip disposed on the flexible printedcircuit FPC1. If the detection electrodes Rx are driven in CDM, aplurality of sensors SE connected to a plurality of detection electrodesRx for each row are formed in the touch sensing chip TSC as shown inFIG. 13. The drive signals output from a plurality of sensors SE aresupplied to a plurality of detection electrodes Rx via a plurality ofdrive signal lines TSpL and the switches SWp. The detection signalsoutput from a plurality of detection electrodes Rx are also supplied toa plurality of sensors SE via a plurality of switches SWp and the drivesignal lines TSpL. The guard signals output from a plurality of sensorsSE are supplied to a plurality of detection electrodes Rx via aplurality of guard signal line TSnL and the switches SWn. A layout ofthe drive signal lines TSpL, the guard signal line TSnL, and the videosignal on the first substrate SUB1 will be explained. FIG. 21A shows awiring layout in a comparative example. An output terminal group 222 isconnected to a plurality of sensors SE (only one sensor SE shown in FIG.21A for convenience of explanations) in the touch sensing chip TSC. Anumber of drive signal lines TSpL and a guard signal line TSnL connectedto the output terminal group 222 extend linearly in the Y direction onthe flexible printed circuit FPC1, and are connected to a Film on Glass(FOG) pad group 224 formed at a connection with the first substrateSUB1. The video signal lines are also formed on the flexible printedcircuit FPC1. Broken lines 210 a and 210 b on the first substrate SUB1represent assemblies of a plurality of video signal lines and are notshown. Though not shown, a plurality of video signal lines 210 a and 210b on the first substrate SUB1 also extend onto the flexible printedcircuit FPC1. Upper ends of the video signal lines 210 a and 210 b areconnected to a selector switch on a glass substrate of the firstsubstrate SUB1, and lower ends of the video signal lines 210 a and 210 bare connected to the signal line driver SD. Since the drive signal linesTSpL and the guard signal line TSnL cannot intersect the video signallines on the flexible printed circuit FPC1, the output terminal group222 connected to a plurality of sensors SE may be provided at an endportion, for example, a right end or a left end inside the touch sensingchip TSC. For this reason, the FOG pad 224 of the flexible printedcircuit FPC1 is also may be provided at the right end or the left.

A number of drive signal lines TSpL and a guard signal line TSnL expandradially from the FOG pad group 224 formed at one position on the firstsubstrate SUB1 and are connected to the switches SWp and SWn. Theswitches SWp and SWn are connected to the detection electrodes. If theFOG pad group 224 is provided at the right end, the signal lines fromthe FOG pad group 224 to the left switches SWp and SWn are long. Thelong signal line has a high resistance value. For example, if the totalnumber of drive signal lines TSpL and the guard signal line TSnL isthirty-six, the total of the resistance values of thirty-six drivesignal lines TSpL and guard signal line TSnL connected to the switchesSWp and SWn of thirty-six sensors SE can be obtained as mentioned below.The resistance values of the drive signal lines and the guard signalline are desirably low.

$\begin{matrix}\begin{matrix}{{{Total}\mspace{14mu} {of}\mspace{14mu} {resistance}\mspace{14mu} {values}} = {\left( {R \times L1} \right)/\left( {D/\left( {L{1/\left( {{L\; 1} +} \right.}} \right.} \right.}} \\\left. {\left. {\left. {L\; 2} \right) \times N} \right) - {Sep}} \right) \\{\approx {555\mspace{14mu} \Omega}}\end{matrix} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

R is a sheet resistance of the wiring layer of the drive signal lineTSpL, L1 and L2 are parameters for defining an X-directional position ofthe FOG pad group 224, D is a Y-directional length of the drive signallines TSpL/guard signal line TSnL on the first substrate SUB1, Sep is aseparation between the lines of the drive signal lines TSpL/guard signalline TSnL, and N is the total number (36 in this example) of drivesignal lines TSpL/guard signal line TSnL.

In the embodiment, since the area of the video signal lines 210 a and210 b is divided into two areas in the X direction, three FOG pad groups224 a, 224 b, and 224 c of the flexible printed circuit FPC1 areseparated at three positions, for example, a center, a left end, an aright end as shown in FIG. 21B. If the total number of drive signallines TSpL and the guard signal line TSnL is thirty-six, eighteen FOGpads form a FOG pad group 224 b at the center, nine FOG pads from a FOGpad group 224 a at the left end, and nine FOG pads form a FOG pad group224 c at the right end. The output terminal group of the touch sensingchip TSC connected to the sensor SE is also divided into three outputterminal groups 222 a, 222 b, and 222 c connected to nine drive signallines/guard signal line, eighteen drive signal lines/guard signal line,and nine drive signal lines/guard signal line. The output terminalgroups 222 a, 222 b, and 222 c are provided at an end portion, forexample, a right end or a left end inside the touch sensing chip TSC,similarly to the comparative example.

Nine drive signal lines/guard signal line from the output terminal group222 c extend linearly in the Y direction on the flexible printed circuitFPC1 and are connected to the FOG pad group 224 c at the right end,further expand radially on the first substrate SUB1 and are connected tothe switches SWp and SWn located on the right side. Eighteen drivesignal lines/guard signal line from the output terminal group 222 bextend linearly in the X direction on the touch sensing chip TSC, extendfrom the center of the touch sensing chip TSC, linearly in the Ydirection on the touch sensing chip TSC, and are connected to the FOGpad group 224 b at the center. Eighteen drive signal lines/guard signalline expand from the FOG pad group 224 b at the center, radially on thefirst substrate SUB1, and are connected to the switches SWp and SWnlocated at the center. Nine drive signal lines/guard signal line fromthe output terminal group 222 a bypass the surrounding (upper, right,lower, and left sides) of the touch sensing chip TSC on the flexibleprinted circuit FPC1, extend linearly in the Y direction along the outeredge of the left end of the touch sensing chip TSC, and are connected tothe FOG pad group 224 a at the left end. Nine drive signal lines/guardsignal line expand radially from the FOG pad group 224 a at the left endand are connected to the switches SWp and SWn located on the left side.

The wiring lengths of the drive signal lines and the guard signal linefrom the FOG pad groups 224 a, 224 b, and 224 c shown in FIG. 21B to theswitches SWp and SWn can be made shorter as compared with those shown inFIG. 21A, by separating the FOG pad groups 224 a, 224 b, and 224 c atthree positions. Thus, if thirty-six drive signal lines and the guardsignal line are classified into nine, eighteen, and eight signal lines,the total of the resistance values of the drive signal lines TSpL andthe guard signal line TSnL becomes small, i.e., approximately 50Ω atmaximum since L1 of (Equation 3) becomes shorter. If the FOG pad groupis not provided at the center but the FOG pad groups are provided at twopositions, i.e., right and left ends and thirty-six drive signal linesand the guard signal line are classified into eighteen signal lines andeighteen signal lines, the total of the resistance values of the drivesignal lines and the guard signal line is approximately 135Ω, though notillustrated in the drawing.

As shown in FIG. 3, three wiring layers WL1, WL2, and WL3 are arrangedin order on the insulating substrate 10, on the first substrate SUB1.The scanning lines GL are formed in the wiring layer WL1 which is thelowest and closest to the insulating substrate 10. The signal lines SLare formed in the wiring layer WL2. The common lines CML and the thirdmetal lines 3M are formed in the uppermost wiring layer WL3.

FIGS. 22A, 22B, and 22C show a layout of the drive signal lines TSpL,the guard signal line TSnL, and the video signal lines on the firstsubstrate SUB1 in a case where the FOG pad groups are disposedseparately at three positions, i.e., the center, the left end, and theright end as shown in FIG. 21B.

In the example shown in FIG. 22A, the drive signal lines TSpL and theguard signal line TSnL are formed of the third metal lines 3M (see FIG.3) in the wiring layer WL3, and the video signal lines 210 a and 210 bare formed of the signal lines SL (see FIG. 3) in the wiring layer WL2.Thus, since the drive signal lines TSpL, the guard signal line TSnL, andthe video signal lines are formed in different wiring layers of thefirst substrate SUB1, the drive signal lines TSpL and the guard signalline TSnL expanding radially from the FOG pad groups 224 a, 224 b, and224 c to the switches SWp and SWn can be formed on the video signallines 210 a and 210 b similarly to the signal lines shown in FIG. 21B.

In FIG. 22A, the video signal lines 210 a and 210 b are formed of asingle-layer wiring, but the video signal lines may be multilayered. Forexample, the video signal lines may be formed of a two-layer structurecomposed of the signal lines SL of the wiring layer WL2 and the thirdmetal lines 3M of the wiring layer WL3 or a three-layer structurecomposed of the scanning lines GL of the wiring layer WL1, the signallines SL of the wiring layer WL2, and the third metal lines 3M of thewiring layer WL3. In this case, the drive signal lines TSpL and theguard signal line TSnL formed of the same wiring layer as the videosignal lines cannot be formed on the video signal lines, and the drivesignal lines TSpL and the guard signal line TSnL are formed whileavoiding the video signal lines as shown in FIG. 22B or FIG. 22C.

In the example shown in FIG. 22B, the drive signal lines TSpL and theguard signal line TSnL are formed of the signal lines SL of the wiringlayer WL2, and the video signal lines 210 a and 210 b are formed of thesignal lines SL of the wiring layer WL2 at most parts, but are partiallyformed of a two-layer structure. For example, the video signal linesaligned at constant intervals in the X direction are formed of twolayers by the signal lines SL of the wiring layer WL2 and the thirdmetal lines 3M of the wiring layer WL3. For this reason, theY-directional length of the area where the video signal lines 210 a and210 b are formed, i.e., the width of the frame area is made smaller thanthat in the example shown in FIG. 22A. Thus, since the drive signallines TSpL, the guard signal line TSnL, and the video signal lines areformed similarly in the wiring layer WL2 of the first substrate SUB1,the drive signal lines TSpL and the guard signal line TSnL cannot beexpanded radially from the FOG pad groups 224 a, 224 b, and 224 c to theswitches SWp and SWn, on the video signal lines 210 a and 210 b, unlikethe signal lines shown in FIG. 21B. For this reason, as shown in FIG.22B, the drive signal lines TSpL and the guide signal line TSnL from theleft and right FOG pad groups 224 a and 224 c are disposed to bypass thevideo signal lines 210 a and 210 b along the surrounding of the areawhere the video signal lines 210 a and 210 b are formed. The drivesignal lines TSpL and the guide signal line TSnL are connected from theupper side (closer to the display area DA) of the area where the videosignal lines 210 a and 210 b are formed to the left and right switchesSWp and SWn. The drive signal lines TSpL and the guide signal line TSnLfrom the central FOG pad group 224 b extend linearly in the Y directionbetween the areas where the video signal lines 210 a and 210 b areformed. The drive signal lines TSpL and the guide signal line TSnL areconnected from the upper side (closer to the display area DA) of thearea where the video signal lines 210 a and 210 b are formed to theswitches SWp and SWn at the center. The video signal lines 210 a and 210b are connected from the upper end to the switches SWp and SWn by thewirings in the scanning line GL layer of the first substrate SUB1.

In yet another example shown in FIG. 22C, the drive signal lines TSpLand the guard signal line TSnL are formed of the third metal lines 3M ofthe wiring layer WL3, the video signal lines 210 a and 210 b are formedof the signal lines SL of the wiring layer WL2 at most parts but thevideo signal lines 210 a and 210 b are formed of the two-layer structureby the signal lines SL of the wiring layer WL2 and the third metal lines3M of the wiring layer WL3, in several parts of the areas 220 a and 220b. For this reason, the width of the frame can be made smaller than thatin the example shown in FIG. 22A, similarly to the example shown in FIG.22B. The drive signal lines TSpL and the guard signal line TSnL from theFOG pad groups 224 a, 224 b, and 224 c are formed radially on the videosignal lines 210 a and 210 b other than the areas 220 a and 220 b so asnot to cover the areas 220 a and 220 b.

FIG. 23A is a plan view showing the area 220 a (similar to 220 b) shownin FIG. 22C. Solid lines represent the video signal lines composed ofthe signal lines SL of the wiring layer WL2, and broken lines representthe video signal lines composed of the third metal lines 3M of thewiring layer WL3. Thus, the video signal lines composed of the signallines SL of the wiring layer WL2 are partially connected to the metallines 3M of the wiring layer WL3, in the middle, and formed of thetwo-layer structure. FIG. 23B and FIG. 23C show enlarged views of “b”area and “c” area shown in FIG. 23A. In FIG. 23B and FIG. 23C, solidlines represent the video signal lines composed of the third metal lines3M of the wiring layer WL3, and broken lines represent the video signallines composed of the signal lines SL of the wiring layer WL2.

Summary of Embodiments

According to the embodiments, the following display device is provided.

-   -   (1) A display device comprising:    -   a display unit comprising electrodes Rx/CE two-dimensionally        arrayed on a substrate SUB1;    -   a touch sensor SE configured to supply drive signals for touch        detection to the electrodes Rx/CE and receive signals from the        electrodes Rx/CE; and    -   a switch circuit group SWG comprising transistors SWd, SWn, and        SWp connected between the touch sensor SE and the electrodes        Rx/CE to select at least one of the electrodes, wherein    -   the transistors SWd, SWn, and SWp comprises a first transistor        164 connected to a first electrode of the electrodes Rx/CE via a        line of a first length and a second transistor 161 connected to        a second electrode of the electrodes Rx/CE via a line of a        second length longer than the first length, and    -   a channel width W1 of the first transistor 164 is smaller than a        channel width W2 of the second transistor 161.    -   (2) The display device of (1), wherein    -   the substrate SUB1 includes a display area DA and a frame area        on a periphery of the display area DA,    -   the display unit is formed in the display area DA, and    -   the switch circuit group SWG is formed in the frame area.    -   (3) The display device of (2), wherein    -   the touch sensor SE is formed on a flexible printed circuit FPC1        connecting the substrate SUB1 and a host device.    -   (4) The display device of (3), wherein    -   the flexible printed circuit FPC1 comprises pads connected to        the electrodes Rx/CE at a portion of connection to the substrate        SUB1,    -   the touch sensor SE comprises detectors which are connected to        the pads via signal lines, the detectors configured to supply        drive signals to the pads and detect signals from the electrodes        Rx/CE,    -   the pads are provided at two or more positions.    -   (5) The display device of (4), wherein    -   video signal lines configured to supply video signals to the        electrodes Rx/CE are formed on the substrate SUB1,    -   the video signal lines are formed in two areas, and    -   the pads are provided between the two areas and an outer side of        the two areas.    -   (6) The display device of (5), wherein    -   the substrate SUB1 comprises wiring layers,    -   the video signal lines are formed in a first wiring layer,    -   the signal lines are formed in a second wiring layer, and    -   the signal lines are formed to overlap the video signal line.    -   (7) The display device of (5), wherein    -   the substrate SUB1 comprises wiring layers,    -   the video signal lines comprise a potion formed in a first        wiring layer and a portion formed in the first wiring layer and        the second wiring layer,    -   the signal lines are formed in the first wiring layer or the        second wiring layer, and    -   the signal lines do not overlap the video signal lines and are        formed while bypassing the video signal lines.    -   (8) The display device of (2), further comprising:    -   a control signal generator CPG formed in the frame area and        configured to control conduction of the transistors.    -   (9) The display device of (8), wherein    -   the control signal generator CPG is configured to simultaneously        select a second number of electrodes Rx/CE, of a first number of        electrodes Rx/CE arranged in a row, and change the selected        electrodes Rx/CE to drive the second number of electrodes Rx/CE,        based on a coding pattern, and    -   the touch sensor SE is configured to operate signals from the        first number of electrodes Rx/CE, based on an inverse matrix of        the coding pattern.    -   (10) The display device of (1), wherein    -   the touch sensor SE is configured to detect variation in        electric capacitance of the electrodes Rx/CE in accordance with        presence of an external object.    -   (11) The display device of (1), wherein    -   the touch sensor SE comprises detectors,    -   each of the detectors is connected to electrodes Rx/CE arranged        in each row, electrodes Rx/CE arranged in each column, or        electrodes Rx/CE arranged in plural rows and plural columns.    -   (12) A display device comprising:    -   a display unit comprising electrodes Rx/CE two-dimensionally        arrayed on a substrate SUB1;    -   a touch sensor SE configured to supply drive signals for touch        detection to the electrodes Rx/CE and receive signals from the        electrodes Rx/CE, the touch sensor being formed on a flexible        printed circuit FPC1 connecting the substrate SUB1 and a host        device; and    -   a switch circuit group SWG comprising transistors SWd, SWn, and        SWp connected between the touch sensor SE and the electrodes        Rx/CE to select at least one of the electrodes Rx/CE, wherein    -   the flexible printed circuit FPC1 comprises pads connected to        the electrodes Rx/CE at a portion of connection to the substrate        SUB1,    -   the touch sensor SE comprises detectors which are connected to        the pads via signal lines, the detectors configured to supply        drive signals to the pads and detect signals from the electrodes        Rx/CE, and    -   the pads are provided at two or more positions.    -   (13) The display device of (12), wherein    -   video signal lines configured to supply video signals to the        electrodes Rx/CE are formed on the substrate SUB1,    -   the video signal lines are formed in two areas, and    -   the pads are provided between the two areas and an outer side of        the two areas.    -   (14) The display device of (13), wherein    -   the substrate SUB1 comprises wiring layers,    -   the video signal lines are formed in a first wiring layer,    -   the signal lines are formed in a second wiring layer, and    -   the signal lines are formed to overlap the video signal lines.    -   (15) The display device of (13), wherein    -   the substrate SUB1 comprises wiring layers,    -   the video signal lines comprise a potion formed in a first        wiring layer and a portion formed in the first wiring layer and        the second wiring layer,    -   the signal lines are formed in the first wiring layer or the        second wiring layer, and    -   the signal lines do not overlap the video signal lines and are        formed while bypassing the video signal lines.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A display device comprising: a substrate; a firstcommon electrode arranged in a first row on a first layer on thesubstrate; a second common electrode arranged in a second row on thefirst layer; a plurality of the pixel electrodes arranged over the firstcommon electrode and the second common electrode; an insulating layerarranged between the plurality of the pixel electrodes and the firstcommon electrode and between the plurality of the pixel electrodes andthe second common electrode; a first line having a first terminal andthe second terminal, the first terminal connected to the first commonelectrode; a second line having a first terminal and the secondterminal, the first terminal connected to the second common electrode; afirst transistor connected to the second terminal of the first line; anda second transistor connected to the second terminal of the second line,wherein the first common electrode, the second common electrode, and theplurality of the pixel electrodes are arranged in a display area, thefirst transistor and the second transistor are arranged outside thedisplay area, the second line is longer than the first line, and achannel width of the first transistor is smaller than a channel width ofthe second transistor.
 2. The display device of claim 1, furthercomprising: a touch sensor circuit configured to supply drive signalsfor touch detection to the first common electrode and the second commonelectrode and to receive signals from the first common electrode and thesecond common electrode.
 3. The display device of claim 2, wherein thetouch sensor circuit is formed on a flexible printed circuit connectingthe substrate and a host device.
 4. The display device of claim 3,further comprising: a control signal generator configured to controlconduction of the first transistor and the second transistor.
 5. Adisplay device comprising: a first substrate; a first electrode arrangedin a first row on a first layer on the first substrate; a secondelectrode arranged in a second row on the first layer; a first linehaving a first terminal and a second terminal, the first terminalconnected to the first electrode; a second line having a first terminaland a second terminal, the first terminal connected to the secondelectrode; a first transistor connected to the second terminal of thefirst line; a second transistor connected to the second terminal of thesecond line; a second substrate; and a liquid crystal layer arrangedbetween the first substrate and the second substrate, wherein the firstelectrode and the second electrode are arranged in a display area, thefirst transistor and the second transistor are arranged outside thedisplay area, the second line is longer than the first line, and achannel width of the first transistor is smaller than a channel width ofthe second transistor.
 6. The display device of claim 5, furthercomprising: a touch sensor circuit configured to supply drive signalsfor touch detection to the first electrode and the second electrode andto receive signals from the first electrode and the second electrode. 7.The display device of claim 6, wherein the touch sensor circuit isformed on a flexible printed circuit connecting the first substrate anda host device.
 8. The display device of claim 7, further comprising: acontrol signal generator configured to control conduction of the firsttransistor and the second transistor.
 9. The display device of claim 5,wherein the second substrate includes an insulating substrate having alight transmitting property.
 10. The display device of claim 9, whereinthe second substrate includes color filters, an overcoat layer, analignment film, a conductive film, and a black matrix.